int removeElement(int* nums, int numsSize, int val) {
    //快慢指针
    int i = 0, j = 0;
    while(j < numsSize){
        if(nums[j] != val){
            nums[i] = nums[j];
            i++; j++;
        }
        else{
            j++;
        }
    }
    return i;
    //爽!!!
}